Alpha release notes draft

From PostgreSQL wiki

The third alpha release for PostgreSQL version 9.1, 9.1alpha3, is now
available. This alpha release contains several new major features added
since the alpha2 release. Please download, install, and test it to give
us early feedback on the features being developed for the future
versions of PostgreSQL.

Features added in 9.1alpha3 since alpha2 include:

KNN GiST, otherwise known as order-by-operator support for GiST, to optimize nearest-neighbor searches

Alpha releases are not stable and should never be used in production;
they are for testing new features only. There is no guarantee that any
features or APIs present in the alphas will be present, or the same, in
the final release.